The present invention relates generally to medical instruments, and more particularly to a safety-disposable medicinal syringe. Still more particularly, the present invention relates to a disposable syringe having a releasable needle hub which, when released, is actuated by ambient air pressure into retraction into an evacuated plunger, carrying the needle with it.
A problem for doctors, nurses, and other health care personnel who use or handle medicinal syringes is accidental puncture of the skin by the needle. The problem can be very serious if the needle has been used. Potentially fatal diseases, such as hepatitis or Acquired Immune Deficiency Syndrome (AIDS), can be contracted if the needle has been used on an infected subject.
The syringe needle is typically covered with a removable sheath prior to and following use to prevent accidental contact, but the act of replacing the sheath after use can still result in accidental skin puncture. Also, if the sheath is not securely repositioned, the danger exists that personnel subsequently involved in disposal of the device may become infected by accidental puncture.
Solutions that attempt to better protect the health care worker include that disclosed in U.S. Pat. No. 4,790,822. The '822 patent discloses a disposable syringe in which the needle can be first captured by the plunger and then withdrawn into the barrel in a position with the needle completely protected by the barrel. The plunger can then be broken off, leaving the broken end flush with the end of the barrel, so that the needle cannot be accidentally pushed out from the barrel and exposed.
U.S. Pat. No. 4,747,830 discloses a similar system, with a plunger that can be broken off once the needle is retracted into the barrel. U.S. Pat. Nos. 4,692,156 and 4,675,005 both disclose disposable syringes wherein the needle can be retracted into the barrel. U.S. Pat. No. 4,643,200 discloses a similar system, used with a blood donor assembly, which allows retraction of a needle into a barrel.
U.S. Pat. No. 4,425,120 discloses a needle guard movable on the syringe barrel between an extended position in which the needle guard shields the needle and a retracted position in which the needle is exposed for use. U.S. Pat. No. 4,816,022 discloses a syringe with a sliding cap for preventing accidental puncture. The '022 patent utilizes a nub and backseat for engagement of a nosepiece for securing the cap around the syringe for safety purposes. U.S. Pat. No. 3,008,570 discloses use of a removable cap for the purpose of enclosing and protecting a sterilized syringe in a transport. U.S. Pat. No. 4,840,619 discloses a syringe assembly that has a transport held in telescoping position over a syringe by flanges. Other and various means of sheathing or shielding a syringe are shown in the following U.S. Pat. Nos. 4,738,663; 4,723,943; 4,666,435; 4,655,751; 4,639,249; 4,592,744; 4,356,822; 4,300,678; 3,976,069; 3,895,633; 3,107,785. U.S. Pat. No. 4,826,483 discloses a non-reusable syringe with a one-way movable piston.
The present invention improves upon these devices by providing a means of automatically, without the need of unusual manipulation, rendering a used syringe safe for handling immediately after use and throughout subsequent disposal procedures, as well as rendering it unsuitable for further use.